The present invention relates to sensors, more specifically to an electrostatic capacitance tilt angle sensor, installed in a measuring instrument or a vehicle to detect the tilt angle.
Japanese Laid-Open Patent Publication No. 08-261757 describes a prior art example of an electrostatic capacitance tilt angle sensor. The electrostatic capacitance tilt angle sensor includes an oil case, a liquid electrostatic capacitance medium contained in the oil case, and two differential electrodes and two common electrodes arranged in the oil case. The parts of the two differential electrodes and the two common electrodes immersed in the electrostatic capacitance medium each configure two capacitors. When the electrostatic capacitance tilt angle sensor is in a horizontal state, the parts of each differential electrode immersed in the electrostatic capacitance medium have substantially the same area (immersed area). Thus, the capacitors have substantially the same electrostatic capacitances. When the electrostatic capacitance tilt angle sensor is tilted, the immersed area of one of the differential electrode increases and the immersed area of the other one of the differential electrodes decreases. This produces a difference between the electrostatic capacitances of the capacitors. The electrostatic capacitance tilt angle sensor calculates the tilt angle based on the difference between the electrostatic capacitances.
The conventional electrostatic capacitance tilt angle sensor has a volume of several cubic centimeters to more than a hundred cubic centimeters and is thus relatively large. There has been a recent demand for a smaller electrostatic capacitance tilt angle sensor that occupies less space. However, when the electrostatic capacitance tilt angle sensor is simply made smaller, the detection reliability and detection resolution fall due to the decrease in electrostatic capacitance and the influence of the surface tension of the electrostatic capacitance medium on the inner wall surface of the oil case.